The invention pertains to methods of forming oxide regions over semiconductor substrates, and in particular embodiments pertains to methods of forming two or more transistors associated with a semiconductor substrate.
Oxide regions, such as, for example, silicon dioxide regions, have numerous applications in semiconductor devices. For instance, a thin layer of silicon dioxide is frequently placed between the conductive material of a transistor gate and an underlying semiconductor substrate, with such layer of silicon dioxide frequently being referred to as so-called xe2x80x9cgate oxidexe2x80x9d. The thickness of the gate oxide can affect various electrical properties of a transistor structure incorporating the gate oxide, and accordingly it is desired to control the gate oxide thickness during device fabrication.
Transistor devices which are commonly used in semiconductor assemblies are PMOS transistor devices and NMOS transistor devices. Each type of transistor device has particular electrical properties associated therewith, and accordingly there can be advantages in utilizing different gate oxide structures for some of the transistor devices associated with a semiconductor structure relative to others of the transistor devices associated with a semiconductor structure.
In light of the importance of gate oxide structures in semiconductor device fabrication, it is desired to develop new methods for forming oxide regions associated with semiconductor structures.
In one aspect, the invention encompasses a method of forming an oxide region over a semiconductor substrate. A nitrogen-containing layer is formed across at least some of the substrate. After the nitrogen-containing layer is formed, an oxide region is grown from at least some of the substrate. The nitrogen of the nitrogen-containing layer is dispersed within the oxide region.
In another aspect, the invention encompasses a method of forming a pair of transistors associated with a semiconductor substrate. A substrate is provided. A first region of the substrate is defined, and additionally a second region of the substrate is defined. The first region is a p-type doped region, and the second region is an n-type doped region. A first oxide region is formed which covers at least some of the first region of the substrate, and which does not cover any of the second region of the substrate. A nitrogen-comprising layer is formed across at least some of the first oxide region and across at least some of the second region of the substrate. After the nitrogen-comprising layer is formed, a second oxide region is grown from the second region of the substrate. A first transistor gate is formed over the first oxide region, and a second transistor gate is formed over the second oxide region. First source/drain regions are formed proximate the first transistor gate to form a PMOS transistor comprising the first transistor gate. Second source/drain regions are formed proximate the second transistor gate to form an NMOS transistor comprising the second transistor gate.